Looking for genes encoding strigolactones receptors in fungi

The arbuscular mycorrhiza (AM), one of the most widespread symbioses on earth, occurs between the majority of land plants and soil fungi belonging to the Glomeromycota Phylum. The root colonization process by AM fungi is depicted as a chronological series of events including the pre-symbiotic phase, contact, fungal entrance and intra-radical fungal proliferation. During the pre-symbiotic phase, strigolactones (SLs) promote hyphal branching and mitochondrial metabolism. Beside AM fungi, a number of pathogenic fungi, including Botrytis cinerea and Cryphonectria parasitica, are sensitive to SLs. However, the molecular mechanisms of SLs perception in fungi are completely unknown. We searched for the putative homologs of the plant SLs receptor (D14) in the complete genome sequences of the AM fungus Rhizophagus irregularis and of the pathogenic fungus C. parasitica. We built 3D structures of the selected proteins by means of homology modelling and we selected two sequences (called RiD14like and CpD14like) out of 6 retained sequences. These show a noticeable match to D14 in terms of folding and of Root Mean Square Deviation (RMSD) value. Docking analysis provided hints on their binding modes with strigol. To further characterize the two proteins and test their affinity/binding to SLs, we cloned the corresponding full length cDNAs as His-tag fusion into the pHUE and pEAQ vectors to obtain high-level expression in bacteria and in planta, respectively. The interaction between RiD14like and CpD14like and SLs using differential scanning fluorimetry (DSF) and intrinsic fluorescence, and the hydrolytic activity of those proteins is under evaluation.